Franklin County

 June 2008
 

Blanch vegetables before freezing 

For the best quality vegetables, blanch before freezing. Onions and green peppers are the only vegetables that should not be blanched before freezing.

What is blanching and why is it a must. Blanching is the scalding of vegetables in boiling water or steam. Blanching slows or stops the action of enzymes. Up until harvest time, enzymes cause vegetables to grow and mature. If vegetables are not blanched, or blanching is not long enough, the enzymes continue to be active during frozen storage; causing off-colors, off-flavors and toughening. In addition, blanching cleanses the surface of dirt and spoilage organisms, brightens the color and helps retard loss of vitamins. It also wilts or softens vegetables and makes them easier to pack.

Blanching time is crucial and varies with the vegetable and size of the pieces to be frozen. Under-blanching speeds up the activity of enzymes and is worse than no blanching. Over-blanching causes loss of flavor, color, vitamins and minerals. Follow recommended blanching times for specific vegetables (recommendation times).

Boiling Water Blanching. The most convenient way to blanch vegetables is in a large kettle of boiling water. Allow one gallon of water per pound of vegetables. Bring the water to a boil and lower vegetables into the water, allowing the water to continue boiling. Cover and start counting the blanching time.

As soon as blanching is complete, drain the vegetables in a strainer, then plunge the vegetables into a container of ice water. Drain thoroughly and freeze.

Steam blanching. Heating in steam is the recommended method for grated summer squash and sprouts. For broccoli, pumpkin, sweet potatoes and winter squash, both steaming and boiling are satisfactory methods. Steam blanching takes about 1-1/2 times longer than water blanching.

To steam, use a pan with a tight-fitting lid and a basket that holds the food at least three inches above the bottom of the pan. Use 1 to 2 inches of water in the pan, bring to a boil and leave on high throughout the blanching process. Place vegetables in the basket, in a single layer, so that steam reaches all parts quickly. Cover the pan and start counting time as soon as the lid is on. Drain and cool.

Microwave blanching. Research has shown that microwave blanching is not always an effective method, as some enzymes may not be inactivated. This could result in low-quality frozen vegetables with off-colors, off-flavors and poor texture. If blanching is done in a microwave oven, follow individual manufacturer’s instructions. Microwave blanching does not save time or energy.

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		University of Missouri Extension Franklin County Site maintained by: Billie Jo Brenner, brennerbj@missouri.edu Last revised: 07/02/08